京沪线党家庄站8G电码化电路增加S8FMJF的方案

通过对列车发车股道不接码的问题提出,对发码通道、切码电路、闭环电码化电路进行分析,结合电路中存在的此类因素,提出解决和处理方案.     

动态模糊神经网络在船舶航向控制器上的应用

当船舶在海湾、海峡等狭窄海域行驶时,对于船舶航向控制器的可靠性和灵活性均有较高的要求,由于船舶模型的参数受到航速和载重量的影响,因而无法保证航向控制的精确性。本文提出一种船舶模型控制与动态神经网络相结合的方法,提高船舶航向控制器的控制精度和可靠性。设计一种零稳态误差控制器对船舶航向进行控制,同时利用模糊神经网络确定闭环控制系统的极点,并用仿真证明本文提出的方法具有较高的精确性和可靠性。     

成都蜀龙五期预制装配式综合管廊拼缝橡胶密封件形式研究

为使橡胶密封件在拼缝处张开量为10 mm、错位量为12 mm以及在闭合压缩力尽可能小的情况下仍能够满足成都市蜀龙五期预制装配式综合管廊0.21 MPa的防水要求,建立3次Ogden橡胶本构模型,对圆形孔洞和类三角形孔洞2种形式的橡胶密封件进行数值模拟,比较2种形式下橡胶密封件的装配力大小,选择装配力小的橡胶密封件进行防水性能和闭合压力试验。结果表明： 1）圆形孔洞橡胶密封件能够满足蜀龙五期综合管廊的防水要求,密封件闭合压缩力为28.55 kN/m。2）当预制块拼装间隙张开量（错位量）较小时,错位量（张开量）的增大会迅速减小橡胶密封件的耐水压力,且张开量对橡胶密封件耐水压力的影响比错位量大。3）预制块拼装间隙张开量越接近0 mm,加载等间距张开量所需装配力越大。     

柴油机各缸工作不均匀程度对性能的影响分析

利用飞轮处的瞬时转速信号来间接估计柴油机的各缸工作不均匀程度,结合基于电磁阀的时间控制式电控燃油喷射系统,实现了柴油机各缸工作不均匀程度的闭环反馈控制。在此基础上,通过台架试验分析了各缸工作不均匀程度和发动机性能之间的关系。结果表明,在发动机的大负荷工况下,各缸工作不均匀程度对发动机的经济性和烟度排放影响显著,从而验证了实现柴油机分缸均匀性实时检测和闭环控制的重要性。     

Seasonal and inter-annual variations in the surface freshwater flux in the Mediterranean Sea from the ECMWF re-analysis project

Seasonal and inter-annual variations in surface freshwater fluxes in the Mediterranean Sea are examined. Evaporation and precipitation rates are estimated from ERA15, the re-analysis project carried out at the European Center for Medium-Range Weather Forecasts (ECMWF) for the period 1979–1993. A seasonal cycle of river runoff is computed from a recent historical data set. The climatological mean for precipitation (326 mm/yr) is comparable to previous estimates, whereas that for evaporation (920 mm/yr) is low compared to other independent estimates, but regions of high and low evaporation rates are correctly located. The budget reveals an annual mean freshwater deficit in the Mediterranean of 480 mm/yr, lower than previous estimates because of the lower evaporation rate estimated by ECMWF. Consequently, the flows through the straits of Gibraltar and Sicily, deduced from the freshwater budget, are found to be slightly low.Seasonal and inter-annual variabilities of ERA15 precipitation are consistent with those deduced from independent precipitation estimates obtained with SSM/I observations for the 1988–1993 period. ECMWF and satellite estimates both agree on the amplitude of the seasonal cycle. The seasonal cycle of the river runoff has a globally small contribution to the freshwater budget, but is significant in summer when the precipitation is nearly null. The variability of the freshwater flux for the Mediterranean as a whole shows a strong seasonal cycle (amplitude of 50 mm/month), which seems to be mainly controlled by evaporation. The inter-annual variability of the freshwater flux, however, appears to be governed mainly by precipitation. Its amplitude, which is of the order of 50 mm/yr on average but may reach nearly 150 mm/yr for a particular year, is considered to be large but nevertheless not sufficient to explain differences observed in the estimates of the climatological mean freshwater flux proposed by various authors. The freshwater deficit in the Mediterranean Sea has globally increased by nearly 50 mm, mainly because of a decrease in precipitation over this 15-yr period.     

垂直腔面发射半导体激光器输出特性的分析

依据腔量子电动力学中自发辐射增强效应,分析了垂直腔面发射半导体激光器的微腔效应,比较了普通开腔和三维封闭腔中的结果。从理论上推出多量子阱垂直腔面发射半导体激光器的速率方程。并讨论了其输出特性即粒子数反转和光输出随泵浦速度变化的关系,同时也讨论了利用微腔效应进一步降低半导体激光器激射阈值的途径。     

Experimental study of drillship resistance performance in open and closed state of moonpool北大核心CSCD

[Objective] This paper carries out an experimental study of a multi-function dirllship model with moonpool structure in towing tank, aiming at analyzing the effects of the moonpool structure on the ship resistance in open and closure condition.[Methods]Taking a dirllship as the research object, the ship motion response in regular and irregular waves is investigated. The resistance of the ship in hydrostatic water and waves is measured with tension sensors, and the acceleration characteristics of the bow, midship and stern are analyzed by acceleration sensors.[Results]The results indicate that hull resistance under light load conditions is greater when open moonpool, while hydrostatic water resistance with closed moonpool is greater under design load conditions. The closed moonpool in regular waves reduces stern acceleration by 58.2%, bow resistance by 46.7% and heave response by 41.8%. The peak of resistance at the bow in irregular waves is about ten times higher than that at the stern, and the peak of resistance occurs more often when the moonpool is open at the same time.[Conclusions]The experimental study shows that the difference in load conditions changes the waterplane area and affects the hull resistance in hyrostatic water. In contrast, the closure of the moonpool not only reduces acceleration and resistance, but also improves surge and heave. As such, this paper can provide references for the structural design of drillships with moonpools. © 2023 Journal of Nanjing Agricultural University. All rights reserved.